1. Field of the Invention
The present invention relates generally to an elongated electric incandescent lamp characterized by a plurality of filaments being spaced apart from each other by a suitable distance within a bulb which is pervious to light, and more particularly relates to such a lamp which is characterized by its ability to be disposed in any direction, and even in a vertical position, without blackening of the bulb occurring, by disposing a getter in the vicinity of the lamp filament.
2. Description of the Prior Art
There have been proposed and devised various types of elongated electric incandescent lamps wherein a single long filament is contained or suspended in the bulb. In one of these lamps, evacuation is required to avoid heat dissipation (so called "gas loss") and excessive increasing of the temperature of the bulb-top by the convection of a filling gas. However, the lamp efficiency and lamp life are not satisfactory because of the low filament-color temperature.
Another elongated electric incandescent lamp having a single long filament disposed in a quartz bulb of which the diameter is less than 10mm, to avoid the gas loss, is already known. While this lamp has been improved, at least as to the problem of "gas loss", it still has the disadvantage, already described, as to gas convection, when the lamp is used while disposed vertically.
Still another elongated electric incandescent lamp having a single long filament disposed in a quartz bulb, such as a halogen lamp, which is often equipped in a copying machine, is also known. In the halogen lamp, the filament is generally designed so as to provide a uniform illumination pattern on the copying paper by terminating several parts thereof. At the terminating parts, or unlighted places, due to the low temperature, the so called "halogen cycle" is disturbed and bulb-blackening arises.